Power harvesting using induction pick-up from the magnetic field surrounding a power distribution line can be used to provide power to distribution line monitoring sensors. Typically, the power line is routed through a current transformer whereby an AC signal is derived from the magnetic field induced by the AC current flow in the distribution line. The AC signal is converted to DC as part of the power harvesting process and used to power the monitoring sensors and associated electronics. This is typically referred to as “inductive harvesting using current transformers.”
One method of mounting the current transformer (C.T.) on the distribution line is to cut the C.T. in two, mount the halves around the uncut distribution line, and mechanically hold the two C.T. halves together. Because the changing magnetic field (AC) causes the magnetic force of attraction between halves of a split core current transformer to alternate between a zero force and a peak force at twice the AC line frequency, the core halves need to be mechanically held together, which can be challenging in a hot-stick deployed sensor application.
Such current transformers, when combined with power conversion circuitry, can provide power to the internal circuitry of the sensor.
A power converter, as typically connected to an electrical source, needs to be designed to operate over a range of inputs appropriate for that application. Common cord-connected equipment, for example, might have a requirement to operate with an input that may vary 10% from a certain nominal voltage. Likewise, electrical devices in automobiles operate over a certain range of allowable inputs voltages. Power line sensors, however, have a challenging requirement because of their need to operate over very wide ranges of inputs. For example, a sensor may be specified to operate from 5 amps to 1000 amps. Designing sensors for such applications require specialized circuitry to provide the stable, fixed power to operate the internal circuitry.